According to SINTEF, enough concrete constructions are built each year worldwide to exceed the height of Mount Everest (equivalent to a 10,000 metre-high concrete block covering one square kilometer). Photo: Thinkstock.

Eco-cement from Norwegian clay

Blue clay from Norway is emerging as a climate-friendly alternative to cements used to make concrete – turning a waste material into a resource.

ECO-CONCRETE: Since the lime cement industry alone is responsible for between five and eight per cent of annual global CO2 emissions, the search is always on to find suitable substitutes.

FACTS

The cement industry is the world's third biggest eco-villain. It is responsible for between five and eight per cent of annual global CO2 emissions.

This is not because cement in itself produces high emissions levels per unit weight. It is simply that there is so much of it. Besides, the cement industry is working constantly to reduce its emissions levels.

According to SINTEF, enough concrete constructions are built each year worldwide to exceed the height of Mount Everest (equivalent to a 10,000 metre-high concrete block covering one square kilometre).

In recent years we have found out that burnt clay can replace up to 50 per cent of the cement mixed into concrete used for construction.

“Clay is simply a major unexploited resource that may help to improve the global environmental picture”, says SINTEF researcher Harald Justnes.

“We’ve known for a while now that pure kaolin clays, which are abundant in warmer climes, are suitable as concrete ingredients. But now we’ve discovered that even impure clays, such as those we have here in Norway, can also fit the bill”, he says.

Eco-cement using burnt clay

Research has also been carried out into other cement substitutes, but right now clay is the future, according to scientists. Photo: SINTEF

The manufacture of cement involves subjecting limestone to heat treatments in excess of 1450 degrees. This causes the rock to release CO2 which alone makes up about 60 per cent of the total emissions. The rest is derived from the fuel used to drive the process.

Burnt clay is more eco-friendly because it doesn’t give off CO2 during heat treatment, other than those emissions resulting from the heating process. However, the volumes are much lower because the clay doesn’t need to be heated to more than between 600 and 800 degrees. Moreover, it’s possible to use bio-fuels, which reduce CO2 emissions even further.

A new life in concrete

Norwegian blue clay consists of a mixture of the clay minerals kaolin, illite and smectite, together with crystalline quartz. Many people have previously dismissed such clays as cement substitutes, not least because of their illite content. This mineral is very slow to react, and many believe that smectite is only marginally reactive. Most people thought that using blue clay was impossible, but SINTEF researchers have now discovered how such clays can have a new life in concrete.

FACTS

When pure tropical kaolin clays are calcinated at about 600 degrees they produce so-called meta-kaolin which has been used as a cement substitute for many years. Because of its white colour, pure kaolin has other valuable applications such as in the manufacture of porcelain, paper and cosmetics.

Except for niche applications, kaolin clay in its refined form will be much too expensive to import into Norway as a cement substitute. Justnes believes that if we want to do something about the large volumes of concrete, then we will have to start thinking in terms of ordinary blue clay.

Just as it comes

Justnes tells Gemini that a major benefit of Norwegian clay is that it requires no refinement before use. It is much less expensive to produce and, in contrast to kaolin clays, currently has no competing applications.

“We can simply dig it out of the ground and heat treat it just as it comes”, says Justnes. “We’re talking about the everyday blue clay that is found pretty much all over Norway. It’s peculiar how it works so well considering that it contains so many contaminants”, he says.

As far as consistency goes it will be possible to replace 50 percent of lime cement with clay. However, in order to protect the concrete’s reinforcement against corrosion, by which he means fracturing resulting from rust formation, Justnes believes the clay fraction should be limited to 35 per cent until more is known.

“We need a lot more evidence before we can come to a conclusion about this”, he says. “And since each clay type behaves a little differently, we also need more research in order to optimise the heat treatment process and find out how the clay responds both in the short and long term”, says Justnes.

Focusing on clay

This year a major new international conference series was launched to address the use of burnt clay in mixing cements and as a cement substitute in concrete.

FACTS

Here are two examples of how Norwegian clay can be changed from a problem into a resource.

*In many places we first have to remove and dispose of quick clays before we can build houses on the land. In the future, however, we will be able to put the clay to good use instead of having to dispose of it.

*Clay may also constitute the basis of a new industrial sector, such as development of the disused brickworks at Bø in Telemark, where there are major clay deposits with the potential for being put to good use.

“This tells us something about how the research community currently regards clay in terms of a resource”, says Justnes.

Research has also been carried out into other cement substitutes, but right now clay is the future”, he says.

“Rice husk ash and fly ash from coal-fired power stations are examples of other substitutes which have been shown to work. However, there is too little rice available to make a decisive difference except at a local scale, and fly ash of the required quality is starting to become scarce. Besides, it has to be imported”, says Justnes. “It’s also likely that, due to global warming considerations, coal-fired power stations will be phased out in the long term because of the large volumes of CO2 emissions they produce. But clay is found all over the world”, he says.

A new study confirms the efficacy of a new diagnostic tool that utilises ultrasound to measure intracranial pressure following accidents. The technology will now be provided with artificial intelligence so that ambulance personnel can carry out examinations at accident scenes.

MORE NORWEGIAN SCITECH NEWS

LOADING CONTENT

Privacy Policy

The Privacy Statement is about how this website collects and uses visitor information. The statement contains information that you are entitled to when collecting information from our website, and general information about how we treat personal data.The legal owner of the website is the processing officer for the processing of personal data. It is voluntary for those who visit the web sites to provide personal information regarding services such as receiving newsletters and using the sharing and tip services. The treatment basis is the consent of the individual, unless otherwise specified.

1. Web analytics and cookies (cookies)

As an important part of the effort to create a user-friendly website, we look at the user pattern of those who visit the site. To analyze the information, we use the Google Analytics analysis tool.Google Analytics uses cookies (small text files that the site stores on the user's computer), which registers the users' IP address and provides information about the individual user's online movements. Examples of what the statistics give us answers to are; how many people visit different pages, how long the visit lasts, what websites users come from and what browsers are used. None of the cookies allow us to link information about your use of the site to you as an individual.The information collected by Google Analytics is stored on Google servers in the U.S.. The information received is subject to the Google Privacy Policy.An IP address is defined as a personal information because it can be traced back to a particular hardware and thus to an individual. We use Google Analytics's tracking code to anonymize the IP address before the information is stored and processed by Google. Thus, the stored IP address can not be used to identify the individual user.

2. Search

If the webpage has search function, it stores information about what keywords users use in Google Analytics. The purpose of the storage is to improve our information service. The search usage pattern is stored in aggregate form. Only the keyword is saved and they can not be linked to other information about the users, such as the IP addresses.

3. Share / Tips service

The "Share with others" feature can be used to forward links to the site by email, or to share the content of social networking. Tips for tips are not logged with us, but only used to add the tips to the community. However, we can not guarantee that the online community does not log this information. All such services should therefore be used wisely. If you use the email feature, we only use the provided email addresses to resend the message without any form of storage.

4. Newsletter

The website can send out newsletters by email if you have registered to receive this. In order for us to be able to send e-mail, you must register an e-mail address. Mailchimp is the data processor for the newsletter. The e-mail address is stored in a separate database, not shared with others and deleted when you unsubscribe. The e-mail address will also be deleted if we receive feedback that it is not active.

5. Registration, form

The website may have a form for registration, contact form or other form. These forms are available to the public to perform the tasks they are supposed to do.Registration form is for visitors to sign up or register.Contact form is for visitors to easily send a message to the website's contact person.We ask for the name of the sender and contact information for this. Personal information we receive is not used for purposes other than responding to the inquiry.The form is sent as email via Mailgun as a third party solution. The entire submission will be stored at Mailgun for 24 hours. Between 24 hours and 30 days, only mailheader is stored before the submission is deleted after 30 days. The reason for this storage is to confirm whether emails are sent from the website and forwarded to the correct recipient.Once the email is received by the recipient, it is up to the recipient to determine the data processing needs of the email.

6. Page and service functionality

Cookies are used in the operation and presentation of data from websites. Such cookies may contain language code information for languages ​​selected by the user. There may be cookies with information supporting the load balancing of the system, ensuring all users the best possible experience. For services that require login or search, cookies can be used to ensure that the service presents data to the right recipient.